Multiple-blade propeller



Patented Oct. 21, 1930 UNITED STATES PATENT orl-lcr;

CHARLES ARTI EUB WRAGG, F N'YACK-ON-HUDSON, NEW YORK MULTIPLE-BLADE P ROIPELLER Application filed October 26, 1928, Serial No. 315,254, andin Canada April 12, 1928.

This invention forms in part a continua-- losses and similarspeed and efficiency reducin factors.

y introducin two or more, auxiliary blades or Vane-s a jacent one or'bo'th edges of a main propeller bladesand in or near the region ofv turbulence or cavitation, the efiect is to reduce the loss of energy over the entire compounded blade, resulting inv increased efliciency under all conditions.

In air propellers it has been diflicult to coordinate the revolutionary blade speed giving maximum thrust efficiency with the revolutions per minute of the shaft required for maximum engine efiiciency the usual compromise being to run the ropeller with greater, and the engine with f wer number of revolutions per minute than is most desirable in. the respective cases. With my compound propeller however this compromise is practically eliminated because the propeller may be rotated at higher velocity without drop inthe thrust curve. Furthermore, a higher efiiciency can be maintained with my improved construction over a widerrange of anglesat which the blades meet the air; I

A still further'advantage of this invention is the reduction of noise from cooling'fans of all kinds including exhaustion and com ression devices as well as of ordinaryprope lers.

In the ac companying drawing the invention is illustrated as applied for different uses and Fig.1 is a fragmentary face-view of marine propeller having compound blades, each 'consistmg of a main and two auxiliary blades or vanes, on the vacuum side and a third on the pressure side near the leading edge of the main blade; 5 I v Fig. 2 is a-transvers'e section along'line 2+2 of Fig. 1;

Fig. 3 is another cross sectional view'of a I A", integral with the hub H, is in this case compound blade having one main blade and three trailing vanes;

Fig. 4 is a face view of triple blade for an .air propeller with its main blade between the auxiliary blades or vanes;

" Fig. 5 a transverse section along line 55 of Fig. 4; and

Fig; 6 a transverse section of a triple blade suitable for a fan and having two auxiliary vanes at the trailing edge of the main blade.

Referring now particularly to Figs. '1 and 2' of the drawing which show my invention as applied to a marine propeller with one main blade and two or three auxiliary vanes.

The main blade A is mounted on the hub H symmetrically around the radius of the hub axis and its edges are curved'so that it has its greater width about midway between its tip and the axis of the hub. Both the main blade and the vanes are shown ca'mbered but other suitable shape. The

they may take an auxiliary vanes I; and C are placed, the former near the trailing edge and the latter near the leading edge of themain blade A and on thecambered side thereof. On the chord side of the main blade is showna third auxiliary vane B which may be used in conjunction with theauxiliary vane B or without it.

The auxiliary vanes arenarrow with substantially parallel edges and are secured on the hub H so that their edges become substan-' tially parallel with the respective edges of the main blade A. p x

In Fig. 3 is shown a cross-section of a compound blade suitable either for a marine or an aerial propeller or wing. The blade members are shown cambered and with one ortwo auxiliary vanes B and B% .On thecambered side of the main blade A and a'third auxil iaryflvane C adjacent the chord side thereof.

All three auxiliary vanes are shown considerably narrower than the main blade and situatedin or near the region of turbulence \at its trailing edge, it being understood however that any of the auxiliaries maytakeany of the shapes, positions or orientations shown in the other figures.

' In Figs. 4 and 5 is shown a blade'suitable for an aerlal' propeller. The main blade shown with straight trailing andleading edges, converging centerward' with at least one of its edges radial. The auxiliary B and B are both of substantially rectangular shape and narrower than the main blade and rigidly connected with the common hub H", all three blade members being preferably cambered, as

Stream line braces E may be used to still further secure the blade members together.

A blade suitable for a fan is'indicated in Fig. 6, where A represents a main blade, curved and of substantially uniform thickness. Partly overlapping its trailing edge is shown an auxiliary vane B on the convex side of the main blade and a second auxiliary vane G is positioned with its leading edge substantially level with the trailing edge of the main blade so as to partly overlap the vane B. Both the auxiliary vanes H and C are considerably narrower than the main blade or about one-eighth of the latters width. The

advantage 'of using this blade constructionfor fans of all kinds, including compression one blade being edge of the succee ng blade.

3. In a structure of the class described,

.main and auxiliary blades mounted rigidly on a common hub, said auxiliary blades being arranged respectively in front and rear of the main blade and positioned to partly overlap the corresponding edges of the main blade in order to compel an unbroken flow of fluid past the structure, the trailing edge of one lade bein parallel with the leading edge of the succee ing blade.

In testimony whereof I here afiix my s1gnature.

CHARLES ARTHUR WRAGG.

leading edge thereof on its chord side.

parallel with the leading and exhausting devices, ventilating and cool- I ing fans and the like, is the great reduction or practical elimination of all noise, usually found in such apparatus.

By the use of this invention of auxiliary vanes in compound with a main blade, the

pel an unbroken fiow of fluid past the strucactual angle of thepropeller system is able tovary thru a wide range without the characteristic and hitherto unavoidable drop in efficiency.

It is evident that many changes in the details and construction of the device may be made under the scope of the claims;

I claim:

1. In a structure of the class described,

cambered-main and auxiliary blades, said auxiliary blades being permanently arranged respectively in front and rear of the main blade and positioned to slightly overlap the corresponding edges of the main blade to comture, the trailing edge of one blade being parallel with the leading edge of the succeedingblade.

2. In a structure of the class described, rig- 1 idly interconnected main and auxiliary blades, said auxiliary blades being permanently arranged respectively in front and rear of the mainblade and positioned to sllghtly overlap the corresponding. edges of the main bladetocompel anunbroken flow of,

fluid past the structure, the trailing edge of 

